The present invention is directed towards an electronic text display system such as are commonly used for word processing, text composing, and the like. The present invention is particularly useful in connection with electronic text composing systems wherein text information including character information defining the text to be presented, font information defining the style of font in which selected portions of the text are to be presented, and composition information such as column spacing, and the like, are all entered into the system and displayed on a display device such as a CRT. The text information is ultimately transferred to an electronic photocomposer which forms photographic negatives which can be used to make printing plates in what is known as the cold-type process. The photographic negatives contain the characters defining the text to be presented in the desired font style and with the desired composition in accordance with the text information which had been entered into the electronic text composing system.
In prior art text composing systems, such as the Printext composing system sold by IBM, the set of characters or symbols which can be represented on the display medium is limited to one font style. This is a highly limiting feature since the user cannot obtain an accurate representation of the actual font style which will be ultimately produced on the printed page. While special symbols may be displayed on the display medium to indicate the fact that associated characters will ultimately be presented in a specific font style, the actual characters dislayed on the display medium will be formed in a single font style. This requires that the user of the system use his imagination to determine what the final printed page will actually look like. Often a certain composition scheme which appears to be aesthetically pleasing in the single style font displayed on the display medium turns out to be quite unsatisfactory when transferred to the printed page with the actual font style.
In an effort to overcome this drawback, at least one composing system manufactured by Compugraphics utilizes a preview screen to provide a detailed an accurate image of different font styles and weights as they will ultimately appear on the printed page. In this system, however, text data is initially, edited and composed on a standard CRT display capable of illustrating only a single font style. Once the user has completed his editing and composition of the page of text, he can display an accurate image of the composed data on a separate preview screen for review before electronic phototypesetting takes place. The information displayed on the preview screen cannot, however, be edited or recomposed on the preview screen. Accordingly, if the user does not like the composition of the page he must return to the standard CRT display and must recompose the page of data using the single character set. Accordingly, he cannot be sure that the final composition will be satisfactory until he completes his editing and again transfers the information to the preview screen.